#pragma once

#include "util/types.hpp"
#include <string>
#include <algorithm>
#include "util/asm.hpp"

/*
C-style format parser. Appends formatted string to `out`, returns number of characters written.
`out`: mutable reference to std::string, std::vector<char> or other compatible container
`fmt`: null-terminated string of `Char` type (char or constructible from char)
`src`: rvalue reference to argument provider.
*/
template <typename Dst, typename Char, typename Src>
usz cfmt_append(Dst& out, const Char* fmt, Src&& src)
{
	ensure(fmt);

	const usz start_pos = out.size();

	struct cfmt_context
	{
		usz size; // Size of current format sequence

		u8 args;  // Number of extra args used
		u8 type;  // Integral type bytesize
		bool dot; // Precision enabled
		bool left;
		bool sign;
		bool space;
		bool alter;
		bool zeros;

		uint width;
		uint prec;
	};

	cfmt_context ctx{0};

	// Error handling: print untouched sequence, stop further formatting
	const auto drop_sequence = [&]
	{
		out.insert(out.end(), fmt - ctx.size, fmt);
		ctx.size = umax;
	};

	const auto read_decimal = [&](uint result) -> uint
	{
		while (fmt[0] >= '0' && fmt[0] <= '9' && result <= (uint{umax} / 10))
		{
			result = result * 10 + (fmt[0] - '0');
			fmt++, ctx.size++;
		}

		return result;
	};

	const auto write_octal = [&](auto value, u64 min_num)
	{
		if constexpr (sizeof(value) == 16)
		{
			out.resize(out.size() + std::max<u64>(min_num, 129 / 3 - (utils::clz128(value | 1) + 1) / 3), '0');
		}
		else
		{
			out.resize(out.size() + std::max<u64>(min_num, 66 / 3 - (std::countl_zero<u64>(value | 1) + 2) / 3), '0');
		}

		// Write in reversed order
		for (auto i = out.rbegin(); value; i++, value >>= 3)
		{
			*i = static_cast<char>(static_cast<u64>(value) & 7) + '0';
		}
	};

	const auto write_hex = [&](auto value, bool upper, u64 min_num)
	{
		if constexpr (sizeof(value) == 16)
		{
			out.resize(out.size() + std::max<u64>(min_num, 128 / 4 - utils::clz128(value | 1) / 4), '0');
		}
		else
		{
			out.resize(out.size() + std::max<u64>(min_num, 64 / 4 - std::countl_zero<u64>(value | 1) / 4), '0');
		}

		// Write in reversed order
		for (auto i = out.rbegin(); value; i++, value >>= 4)
		{
			*i = (upper ? "0123456789ABCDEF" : "0123456789abcdef")[static_cast<usz>(value & 0xf)];
		}
	};

	const auto write_decimal = [&](auto value, s64 min_size)
	{
		const usz start = out.size();

		do
		{
			if constexpr (sizeof(value) == 16)
			{
				const u128 v0 = value;
				value >>= 1;
				constexpr u128 by_five = 0x3333'3333'3333'3333;
				const u128 v1 = (value >> 64) * by_five;
				const u128 v2 = ((value >> 64) * by_five) >> 64;
				const u128 v3 = (static_cast<u64>(value) * by_five) >> 64;
				value = v1 + v2 + v3;

				out.push_back(static_cast<char>(static_cast<u64>(v0 - (value * 10))) + '0');
			}
			else
			{
				out.push_back(value % 10 + '0');
				value /= 10;
			}
		} while (0 < --min_size || value);

		// Revert written characters
		for (usz i = start, j = out.size() - 1; i < j; i++, j--)
		{
			std::swap(out[i], out[j]);
		}
	};

	// Single pass over fmt string (null-terminated), TODO: check correct order
	while (const Char ch = *fmt++)
		if (ctx.size == 0)
		{
			if (ch == '%')
			{
				ctx.size = 1;
			}
			else
			{
				out.push_back(ch);
			}
		}
		else if (ctx.size == 1 && ch == '%')
		{
			ctx = {0};
			out.push_back(ch);
		}
		else if (ctx.size == umax)
		{
			out.push_back(ch);
		}
		else
			switch (ctx.size++, ch)
			{
			case '-': ctx.left = true; break;
			case '+': ctx.sign = true; break;
			case ' ': ctx.space = true; break;
			case '#': ctx.alter = true; break;
			case '0': ctx.zeros = true; break;

			case '1':
			case '2':
			case '3':
			case '4':
			case '5':
			case '6':
			case '7':
			case '8':
			case '9':
			{
				if (ctx.width) [[unlikely]]
				{
					drop_sequence();
				}
				else
				{
					ctx.width = read_decimal(ch - '0');
				}

				break;
			}

			case '*':
			{
				if (ctx.width || !src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
				}
				else
				{
					const int warg = src.template get<int>(ctx.args++);
					ctx.width = std::abs(warg);
					ctx.left |= warg < 0;
				}

				break;
			}

			case '.':
			{
				if (ctx.dot || ctx.prec) [[unlikely]]
				{
					drop_sequence();
				}
				else if (*fmt >= '0' && *fmt <= '9') // TODO: does it allow '0'?
				{
					ctx.prec = read_decimal(0);
					ctx.dot = true;
				}
				else if (*fmt == '*')
				{
					if (!src.test(ctx.args)) [[unlikely]]
					{
						drop_sequence();
					}
					else
					{
						fmt++, ctx.size++;
						const int parg = src.template get<int>(ctx.args++);
						ctx.prec = std::max(parg, 0);
						ctx.dot = parg >= 0;
					}
				}
				else
				{
					ctx.prec = 0;
					ctx.dot = true;
				}

				break;
			}

			case 'h':
			{
				if (ctx.type) [[unlikely]]
				{
					drop_sequence();
				}
				else if (fmt[0] == 'h')
				{
					fmt++, ctx.size++;
					ctx.type = src.size_char;
				}
				else
				{
					ctx.type = src.size_short;
				}

				break;
			}

			case 'l':
			{
				if (ctx.type) [[unlikely]]
				{
					drop_sequence();
				}
				else if (fmt[0] == 'l')
				{
					fmt++, ctx.size++;
					ctx.type = src.size_llong;
				}
				else
				{
					ctx.type = src.size_long;
				}

				break;
			}

			case 'z':
			{
				if (ctx.type) [[unlikely]]
				{
					drop_sequence();
				}
				else
				{
					ctx.type = src.size_size;
				}

				break;
			}

			case 'j':
			{
				if (ctx.type) [[unlikely]]
				{
					drop_sequence();
				}
				else
				{
					ctx.type = src.size_max;
				}

				break;
			}

			case 't':
			{
				if (ctx.type) [[unlikely]]
				{
					drop_sequence();
				}
				else
				{
					ctx.type = src.size_diff;
				}

				break;
			}

			case 'c':
			{
				if (ctx.type || !src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const usz start = out.size();
				out.push_back(src.template get<Char>(ctx.args));

				if (1 < ctx.width)
				{
					// Add spaces if necessary
					out.insert(out.begin() + start + ctx.left, ctx.width - 1, ' ');
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 's':
			{
				if (ctx.type || !src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const usz start = out.size();
				const usz size1 = src.fmt_string(out, ctx.args);

				if (ctx.dot && size1 > ctx.prec)
				{
					// Shrink if necessary
					out.resize(start + ctx.prec);
				}

				const usz size2 = out.size() - start;

				if (size2 < ctx.width)
				{
					// Add spaces if necessary
					out.insert(ctx.left ? out.end() : out.begin() + start, ctx.width - size2, ' ');
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'd':
			case 'i':
			{
				if (!src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const usz src_type = src.type(ctx.args);

				if (!ctx.type || src_type > 8)
				{
					ctx.type = static_cast<u8>(src_type);

					if (!ctx.type)
					{
						ctx.type = src.size_int;
					}
				}

				// Sign-extended argument expected
				const u64 val = src.template get<u64>(ctx.args);
				bool negative = ctx.type && ctx.type <= 8 && static_cast<s64>(val) < 0;

				if (ctx.type == 16)
				{
					u128 val2 = *reinterpret_cast<const u128*>(val);
					negative = !!(val2 & (u128{1} << 127));
				}

				const usz start = out.size();

				if (!ctx.dot || ctx.prec)
				{
					if (negative)
					{
						out.push_back('-');
					}
					else if (ctx.sign)
					{
						out.push_back('+');
					}
					else if (ctx.space)
					{
						out.push_back(' ');
					}

					if (ctx.type >= 16)
					{
						u128 val2 = *reinterpret_cast<const u128*>(val);
						write_decimal(negative ? u128{} - val2 : val2, ctx.prec);
					}
					else
					{
						write_decimal(negative ? u64{} - val : val, ctx.prec);
					}
				}

				const usz size2 = out.size() - start;

				if (size2 < ctx.width)
				{
					// Add padding if necessary
					if (ctx.zeros && !ctx.left && !ctx.dot)
					{
						out.insert(out.begin() + start + (negative || ctx.sign || ctx.space), ctx.width - size2, '0');
					}
					else
					{
						out.insert(ctx.left ? out.end() : out.begin() + start, ctx.width - size2, ' ');
					}
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'o':
			{
				if (!src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const usz src_type = src.type(ctx.args);

				if (!ctx.type || src_type > 8)
				{
					ctx.type = static_cast<u8>(src_type);

					if (!ctx.type)
					{
						ctx.type = src.size_int;
					}
				}

				const u64 mask =
					ctx.type == 1 ? 0xff :
					ctx.type == 2 ? 0xffff :
					ctx.type == 4 ? 0xffff'ffffu :
									0xffff'ffff'ffff'ffffu;

				// Trunc sign-extended signed types
				const u64 val = src.template get<u64>(ctx.args) & mask;

				const usz start = out.size();

				if (ctx.alter)
				{
					out.push_back('0');

					if (ctx.prec)
					{
						ctx.prec--;
					}
				}

				if ((ctx.alter && val) || !ctx.dot || ctx.prec)
				{
					if (ctx.type >= 16)
					{
						u128 val2 = *reinterpret_cast<const u128*>(val);
						write_octal(val2, ctx.prec);
					}
					else
					{
						write_octal(val, ctx.prec);
					}
				}

				const usz size2 = out.size() - start;

				if (size2 < ctx.width)
				{
					// Add padding if necessary
					out.insert(ctx.left ? out.end() : out.begin() + start, ctx.width - size2, ctx.zeros && !ctx.left && !ctx.dot ? '0' : ' ');
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'x':
			case 'X':
			{
				if (!src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const usz src_type = src.type(ctx.args);

				if (!ctx.type || src_type > 8)
				{
					ctx.type = static_cast<u8>(src_type);

					if (!ctx.type)
					{
						ctx.type = src.size_int;
					}
				}

				const u64 mask =
					ctx.type == 1 ? 0xff :
					ctx.type == 2 ? 0xffff :
					ctx.type == 4 ? 0xffff'ffffu :
									0xffff'ffff'ffff'ffffu;

				// Trunc sign-extended signed types
				const u64 val = src.template get<u64>(ctx.args) & mask;

				const usz start = out.size();

				if (ctx.alter)
				{
					out.push_back('0');

					if (val)
					{
						out.push_back(ch); // Prepend 0x or 0X
					}
				}

				if ((ctx.alter && val) || !ctx.dot || ctx.prec)
				{
					if (ctx.type >= 16)
					{
						u128 val2 = *reinterpret_cast<const u128*>(val);
						write_hex(val2, ch == 'X', ctx.prec);
					}
					else
					{
						write_hex(val, ch == 'X', ctx.prec);
					}
				}

				const usz size2 = out.size() - start;

				if (size2 < ctx.width)
				{
					// Add padding if necessary
					if (ctx.zeros && !ctx.left && !ctx.dot)
					{
						out.insert(out.begin() + start + (ctx.alter && val ? 2 : 0), ctx.width - size2, '0');
					}
					else
					{
						out.insert(ctx.left ? out.end() : out.begin() + start, ctx.width - size2, ' ');
					}
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'u':
			{
				if (!src.test(ctx.args)) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const usz src_type = src.type(ctx.args);

				if (!ctx.type || src_type > 8)
				{
					ctx.type = static_cast<u8>(src_type);

					if (!ctx.type)
					{
						ctx.type = src.size_int;
					}
				}

				const u64 mask =
					ctx.type == 1 ? 0xff :
					ctx.type == 2 ? 0xffff :
					ctx.type == 4 ? 0xffff'ffffu :
									0xffff'ffff'ffff'ffffu;

				// Trunc sign-extended signed types
				const u64 val = src.template get<u64>(ctx.args) & mask;

				const usz start = out.size();

				if (!ctx.dot || ctx.prec)
				{
					if (ctx.type >= 16)
					{
						u128 val2 = *reinterpret_cast<const u128*>(val);
						write_decimal(val2, ctx.prec);
					}
					else
					{
						write_decimal(val, ctx.prec);
					}
				}

				const usz size2 = out.size() - start;

				if (size2 < ctx.width)
				{
					// Add padding if necessary
					out.insert(ctx.left ? out.end() : out.begin() + start, ctx.width - size2, ctx.zeros && !ctx.left && !ctx.dot ? '0' : ' ');
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'p':
			{
				if (!src.test(ctx.args) || ctx.type) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				const u64 val = src.template get<u64>(ctx.args);

				const usz start = out.size();

				write_hex(val, false, sizeof(void*) * 2);

				const usz size2 = out.size() - start;

				if (size2 < ctx.width)
				{
					// Add padding if necessary
					out.insert(ctx.left ? out.end() : out.begin() + start, ctx.width - size2, ' ');
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'f':
			case 'F':
			case 'e':
			case 'E':
			case 'a':
			case 'A':
			case 'g':
			case 'G':
			{
				if (!src.test(ctx.args) || ctx.type) [[unlikely]]
				{
					drop_sequence();
					break;
				}

				// Fallback (TODO)

				const std::string _fmt(fmt - ctx.size, fmt);

				const f64 arg0 = src.template get<f64>(0);
				const u64 arg1 = ctx.args >= 1 ? src.template get<u64>(1) : 0;
				const u64 arg2 = ctx.args >= 2 ? src.template get<u64>(2) : 0;

				if (const usz _size = std::snprintf(nullptr, 0, _fmt.c_str(), arg0, arg1, arg2))
				{
					out.resize(out.size() + _size);
					std::snprintf(&out.front() + out.size() - _size, _size + 1, _fmt.c_str(), arg0, arg1, arg2);
				}

				src.skip(ctx.args);
				ctx = {0};
				break;
			}

			case 'L': // long double, not supported
			case 'n': // writeback, not supported
			default:
			{
				drop_sequence();
			}
			}

	// Handle unfinished sequence
	if (ctx.size && ctx.size != umax)
	{
		fmt--, drop_sequence();
	}

	return out.size() - start_pos;
}
